Mexican feminists are rightly celebrating the recent supreme court's decision to uphold a law that allows legal and free abortion in Mexico City during the first 12 weeks of pregnancy. But what often gets lost in how this is reported is just how recently such things seemed little more than a pipedream.

As little as three years ago, campaigners I talked to would shrug away the very idea of abortion on demand as simply too ambitious a goal to openly articulate in Mexican society.

It was more complicated than the influence of the bishops in an overwhelmingly Catholic country, they would say. It was equally associated with the way the traditionally anti-clerical state (responsible for swinging many a priest from lampposts in the past) had established a live-and-let-live arrangement with the church that rested on the avoidance of controversy. So while conservatives would refrain from campaigning for prosecutions of those involved in illegal terminations, nominally progressive politicians seemed unconcerned that what legal rights to abortions did exist were unenforced, such as in cases of rape.

In the meantime, Mexican woman of any influence had no trouble finding private doctors to perform a discrete and safe procedure. While poor and shame-conscious families could be relied on to keep the haemorrhaging tragedies of the back street conveniently covered up. The most radical pro-choice group I know of concentrated its efforts less on changing the laws than on surreptitiously teaching clandestine practitioners to wear sterilised gloves.

And then, in 2007, everything changed. The same leftwing party in power in the capital for a decade in which it had done little more than tinker with the theoretical restrictions, suddenly changed tack. It passed a bill not only permitting legal abortions in the first trimester, but also obligating city medical services to provide them for free. The issue was suddenly out of the cupboard and the unwritten hush code smashed.

Since then there have been problems finding ways around the many doctors who refuse to perform abortions, and many complaints from women about treatment received from pro-life hospital staff. Nevertheless over 12,000 women have had terminations in public hospitals in the capital since the law went into effect in April last year. And that is a simply extraordinary fact.

Anti-abortionists have, of course, held emotive demonstrations positioning 12,000 little white crosses on a central monument and blaring out foetal heartbeats to passersby, at the same time as the flood gates have been lifted on pronouncements from the pulpit.

But, to the shock of many an observer, these deeply passionate disagreements have been quite manageable. And now the supreme court has thrown out the conservative federal government's argument that the law contravenes the right to life, the political debate on abortion seems unstoppable. And this is what is potentially most important about last week's decision.

Feminists will be newly energised to campaign for similar legislation in other states outside the relatively progressive bubble of the capital. And, I think, they can expect radical pro-life elements of the governing rightwing party to counter by pushing for the prosecution of doctors carrying out illegal terminations. They may well start tabling even more restrictive legislation, although banning all abortion outright, as in Nicaragua, seems unlikely.

I hesitate to predict which side will win these regional political battles, but for the moment let's just relish the fact that they are now on the horizon and the sun will keep rising and setting anyway. The story of the recent advance of abortion rights in Mexico is beginning to sound like a fable for how societies are often much readier to face their taboos than they are given credit for.